I think FatFlyer has it spot on: half speedbrake only is available on the A320 with the AP engaged (not the case for the 318, 319 or 321).
This is correct as regards to the 320 and 321 (I don't know about the other 2).
However, full speedbrake deflection on the A321 is the same angle of deflection as 1/2 speedbrake on the 320.
With AP engaged on the 320, speedbrake angle is proportional to the lever position until the 1/2 way detent. Thereafter any lever movement beyond 1/2 produces no change to the control surface position. Disengaging the AP allows full control of the speedbrakes, proportional to lever position.
On the 321, regardless of the AP condition, you have full control of the speedbrakes throughout the entire range of movement.
Some of our pilots only put the lever into the 1/2 position, I do not as I seem to think that will only give me 1/4 speedbrake
On the 320, this is not correct. With AP engaged, it is pointless moving the lever beyond 1/2 as 1/2 is all you will get. Remember, speedbrake deflection is proportional to lever position until 1/2, so by selecting 1/2, you will get 1/2, NOT a 1/4.
On the 321, if you selected 1/2, you would get 1/2 also, but as the angle of deflection range is only half that of the 320, in effect you would be getting 1/4 of the angle of deflection that would be available at full deflection on the 320.
Clear as mud....
